In recent Townsend Letter articles, I have outlined the benefits of eating a diet keyed to metabolic type. No one diet is ideal for everyone. What is healthful for one person may be inadequate or even harmful for another. When we recommend foods and supplements, it is crucial to address the patient's individual biochemistry. By testing thoroughly to determine each client's metabolic type, my associates and I are able to determine which foods and supplements will be beneficial for that person, and which will be useless or worse.

To properly explain the usefulness of metabolic typing, I must briefly discuss the crucial role of blood pH. The ideal venous pH is 7.461. At this level, the body most efficiently absorbs and utilizes nutrients. A higher or lower pH means the blood is too alkaline or too acid for optimal functioning. Mal absorption and poor utilization of nutrients can lead to an extremely broad array of symptoms, from fatigue and allergies to overweight and high blood pressure. The further the blood deviates from its ideal pH level, the more severe the symptoms become. When the blood moves to its ideal pH level, the body comes into balance and these symptoms generally abate or disappear altogether. The key to managing the blood pH lies in knowing the individual's metabolic type.

There are five basic metabolic types. Two of these tend to be too acid, and need foods that will help move their blood pH towards the alkaline. Two tend to be too alkaline, and need foods to make them more acid. One type tends to be fairly close to the center, yet may need fine-tuning to move to the ideal level. Why not simply determine the patient's blood pH and prescribe foods accordingly? Because even if we know, for example, that the blood is too acid, we still don't know which foods will make it more alkaline. The somewhat surprising reason for this is that any given food may be either alkalinizing or acidifying, depending on the metabolic type of the person ingesting it. Before we can be certain which foods (and supplements) a patient needs, we must know his or her metabolic type.

Recently, there has been a great deal of excitement about another way to eat for your type: eating for your blood type, as described in the work of Peter d'Adamo (see Additional Information at the end of the article:2) This system is very appealing, at least in part because it is so easy to use: once you know your blood type, you simply follow the diet for that type outlined in d'Adamo's book. According to d'Adamo's interesting theory, the various human blood types evolved over time, and each corresponds to a phase of human development, and therefore to the dietary patterns of that period. The first blood type to evolve was type O, which was the blood type of early nomadic humans, hunter-gatherers whose diet included as much meat as they could catch. Then, about fifteen thousand years ago, certain humans learned to grow crops. They settled, became agrarian, and shifted to a more vegetarian, grain-based diet. These peoples evolved blood type A. Further evolution and mingling produced the other two types, B and AB. According to the theory, people with blood type O will function best by eating a lot of meat, while blood type A's will be healthiest when eating a mainly vegetarian diet, and so on. This makes a great deal of sense. The trouble is, it doesn't work.

In my practice I see many type O's who thrive on a meat-based diet. But I also see many type O's who have become unwell on such a diet, and actually need a mainly vegetarian diet in order to feel their best. Conversely, I often see type A's who need to eat a lot of fat and meat to achieve optimal health. Other researchers and practitioners report the same experience: blood type is an unreliable indicator of dietary needs. Robert Crahon, a renowned nutritionist in Boulder, Colorado, has concluded that you cannot simply eat for your blood type. Bill Wolcott of Winthrop, Washington, who has created the Healthexcel program, states that you cannot rely on blood type to determine your most healthful diet and supplements. Dr. Guy Schenker, a chiropractor who runs the Nutrispect Company, is a renowned writer and publishes a monthly newsletter. He too is convinced that "eat for your blood type" is an erroneous prescription. The successes are balanced by too many failures. To be useful, the theory must produce consistent results.

Why does eating for blood type work for some and fail utterly for others? It is impossible to know for certain, but I conjecture that the type O of today is very different from the type O of sixty thousand years ago. At that time, presumably, all humans were type O, and all had evolved to utilize the hunter-gatherer diet. Then one population group split off, adapted to an agrarian diet, and developed type A blood. At this point, each population group was homogeneous, and blood type was probably a reliable indicator of dietary needs. Since that time, I would suggest, human population groups have mingled, creating a very mixed gene pool. Each individual still has one of the four major blood types, but may have characteristics of all four types, passed on with the genes of parents and grandparents. Therefore, the individual physiology may contain elements found in various blood types, in unique combination. One Type O could have a very different metabolism, and dietary profile, from another. Though it is pure conjecture, this is one theory that could help to explain the inconsistency of results from "eating for your blood type."

Eating for your metabolic type is not quite so easy to use - it requires a series of tests to determine type - but the consistent results make it worth the extra trouble. In order to efficiently determine each patient's metabolic type, Bill Wolcott and I have developed a series of tests which can be completed in one office visit. Before the visit, the client is asked to complete a questionnaire which includes both physical and psychological characteristics which are linked to metabolic type. In the office, we take physiological readings, including blood glucose level, pulse, respiratory rate, blood pressure, and several others. In addition, we ask for the patient's subjective experience of well being, energy level, hunger, etc. We then give the patient a high glucose drink. We do this in order to challenge the system, and measure its reactions. We repeat the physiological tests and the subjective questions at specific intervals over the course of the visit. The entire process takes about two hours, and the results, combined with our extensive research data, allow us to determine each patient's metabolic type, with 80% accuracy on the first visit. Further testing, including a protein challenge I have recently developed, helps us to classify the 20% of patients who yield ambiguous results from the standard series of tests (see Additional Information at the end of the article:3).

In order to make the benefits of metabolic typing more widely available, my colleagues and I have developed a two part program for teaching medical and nutritional professionals how to use the system. In the Level One seminar, we outline the entire program, including hands-on practice at performing the tests and interpreting the results. This two-day seminar prepares the participants to begin using metabolic typing with their own patients. Consultation by telephone is available and generally necessary at this stage, until each participant becomes thoroughly proficient at using the system. To this end, we highly recommend that participants follow up by taking the Level Two seminar. In Level Two, we cover in depth the use of supplements as well as foods to resolve imbalances in the system. This information is fairly intricate, as well as extremely useful. In addition, we go through more complicated case studies, adding further details and refinements that cannot be covered in the basic program.